Solar heat collector and solar water heater

ABSTRACT

A solar heat collector includes a container, a transparent cover plate located on the container, a thermal insulation material located inside of the container to form an insulation space, and a heat absorption plate located in the insulation space. The heat absorption plate includes a base and a coating located on the base, and the coating includes a plurality of carbon nanotubes entangled with each other to form a network structure and a plurality of carbon particles in the network structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to commonly-assigned application entitled,“LIGHT ABSORBER PREFORM SOLUTION AND METHOD FOR MAKING THE SAME”,concurrently filed (Atty. Docket No. US83260); “LIGHT ABSORBER ANDMETHOD FOR MAKING THE SAME”, concurrently filed (Atty. Docket No.US83259); “INFRARED DETECTOR AND INFRARED IMAGER”, concurrently filed(Atty. Docket No. US83258); and “INFRARED STEALTH CLOTH AND INFRAREDSTEALTH CLOTHES”, concurrently filed (Atty. Docket No. US83257). Theentire contents of which are incorporated herein by reference.

FIELD

The present application relates to a solar heat collector and a solarwater heater.

BACKGROUND

A solar heat collector is a device that converts the radiant energy fromthe sun into thermal energy. Because solar energy is relativelyscattered, it is necessary to concentrate the solar energy to be useful.Therefore, the heat collector is a key part of various solar energydevices. In different applications, the heat collectors and theirmatching system are categorized into many types with different names,such as a solar cooker for cooking, a solar water heater for producinghot water, a solar dryer for drying an object, and a solar furnace forsmelting metals, a solar house, a solar thermal power station, etc.

The solar collector can generally be categorized into flat-plate solarheat collector and concentrating solar heat collector. The flat-platesolar heat collector is generally used for the solar water heater. Theconcentrating solar heat collector can focus sunlight to achieve highertemperatures, which is used for heating or cooling. Existing solar heatcollectors have various heat loss and low heat absorption rate.Utilization of solar thermal energy can be further improved.

Therefore, there is room for improvement in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof embodiments, with reference to the attached figures, wherein:

FIG. 1 shows a transmission electron microscope (TEM) image of carbonnanotubes dispersed in an ethanol solution in a first embodiment.

FIG. 2 shows a scanning electron microscope (SEM) image of carbon blackpowder with a diameter of 20 microns in the first embodiment.

FIG. 3 shows an optical photograph of 1 gram carbon black powder addedinto a carbon nanotube suspension in the first embodiment.

FIG. 4 shows an optical photograph of 5 grams carbon black powder addedinto the carbon nanotube suspension in the first embodiment.

FIG. 5 shows an optical photograph of 7 grams carbon black powder addedinto the carbon nanotube suspension in the first embodiment.

FIG. 6 shows an optical photograph of a toy without spraying a lightabsorber preform solution in a second embodiment.

FIG. 7 shows an optical photograph of the toy after spraying the lightabsorber preform solution in the second embodiment.

FIG. 8 shows an SEM image of a coated layer formed by spraying a purecarbon nanotube dispersion in the second embodiment.

FIG. 9 shows an SEM image of a quartz substrate after spraying the lightabsorber preform solution in the second embodiment.

FIG. 10 shows another SEM image of the coated layer formed by sprayingthe pure carbon nanotube dispersion in the second embodiment.

FIG. 11 shows an SEM image of a light absorber in the second embodiment.

FIG. 12 shows yet another SEM image of the coated layer formed byspraying the pure carbon nanotube dispersion in the second embodiment.

FIG. 13 shows another SEM image of the light absorber in the secondembodiment.

FIG. 14 shows a reflection spectrum of the light absorber in a visiblelight wavelength range in the second embodiment.

FIG. 15 shows a reflection spectrum of the light absorber in anear-infrared wavelength range in the second embodiment.

FIG. 16 shows a reflection spectrum of the light absorber in amid-infrared wavelength range in the second embodiment.

FIG. 17 shows a reflection spectrum of the light absorber when anincident angle of an incident light is 15 degrees in the secondembodiment.

FIG. 18 shows a reflection spectrum of the light absorber when anincident angle of an incident light is 30 degrees in the secondembodiment.

FIG. 19 shows a reflection spectrum of the light absorber when anincident angle of an incident light is 45 degrees in the secondembodiment.

FIG. 20 shows a reflection spectrum of the light absorber when anincident angle of an incident light is 60 degrees in the secondembodiment.

FIG. 21 shows a thermal imager photograph of the light absorbercontaining 5 g of carbon particles (the light absorber preform solutionis sprayed on a silicon substrate) in the second embodiment.

FIG. 22 shows a time-temperature of the light absorber containing 5 g ofcarbon particles (the light absorber preform solution is sprayed on thesilicon substrate) when exposing the light absorber to sunlight in thesecond embodiment.

FIG. 23 shows an optical photograph of the quartz substrate afterspraying the light absorber preform solution in the second embodiment.

FIG. 24 shows a thermal image captured by an infrared thermal imager inthe second embodiment.

FIG. 25 shows an optical photograph of a water droplet falling on asurface of the light absorber in the second embodiment.

FIG. 26 shows a schematic view of an infrared detector in a thirdembodiment.

FIG. 27 shows a schematic view of an infrared imager in the thirdembodiment.

FIG. 28 shows a schematic view of an infrared stealth cloth in a fourthembodiment.

FIG. 29 shows an optical photograph of the infrared stealth cloth in thefourth embodiment.

FIG. 30 shows an optical photograph of a hand covered by the infraredstealth cloth in the fourth embodiment.

FIG. 31 shows a thermal image of the hand covered by the infraredstealth cloth in the fourth.

FIG. 32 shows a schematic view of an infrared stealth clothes in thefourth embodiment.

FIG. 33 shows a schematic view of a solar heat collector in a fifthembodiment.

FIG. 34 shows a schematic view of a solar water heater in the fifthembodiment.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale, andthe proportions of certain parts may be exaggerated to illustratedetails and features better. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this disclosure will now bepresented.

The term “substantially” is defined to be essentially conforming to theparticular dimension, shape or other word that substantially modifies,such that the component need not be exact. For example, substantiallycylindrical means that the object resembles a cylinder, but can have oneor more deviations from a true cylinder. The term “comprising” means“including, but not necessarily limited to”; it specifically indicatesopen-ended inclusion or membership in a so-described combination, group,series and the like.

The disclosure is illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” embodiment in this disclosure are not necessarily tothe same embodiment, and such references mean at least one.

A light absorber preform solution of a first embodiment includes asolvent, a plurality of carbon nanotubes, and a plurality of carbonparticles. The plurality of carbon nanotubes and the plurality of carbonparticles are located in the solvent. The light absorber preformsolution is a suspension solution.

The plurality of carbon nanotubes form a flocculent structure in thesolvent, and the flocculent structure refers to the plurality of carbonnanotubes are attracted to and entangled with each other through van derWaals forces to form a network structure. The carbon nanotubes are notcompletely dispersed in the solvent, but form the network structure inthe solvent. The carbon nanotubes may be single-walled carbon nanotubes,double-walled carbon nanotubes, or multi-walled carbon nanotubes. In oneembodiment, the carbon nanotubes are multi-walled carbon nanotubes withan average diameter of 20 nm (nanometers).

The plurality of carbon particles is located in the network structure,and each carbon particle is inserted into the network structure andsurrounded or coated by the plurality of carbon nanotubes. Each carbonparticle is embedded into the network structure and trapped between theentangled carbon nanotubes. In one embodiment, some carbon particles arein direct contact with the carbon nanotubes. In one embodiment, aportion of surfaces of some carbon particles is in direct contact withthe carbon nanotubes, and another portion of surfaces of some carbonparticles is exposed and is spaced apart from the plurality of carbonnanotubes. In one embodiment, one portion of each of the plurality ofcarbon particles is in direct contact with the plurality of carbonnanotubes, and the other portion of each of the plurality of carbonparticles is spaced apart from the plurality of carbon nanotubes. Thetype of the carbon particles is not limited, such as carbon black.

The type of the solvent is not limited, such as an organic solvent. Thesolvent can be a volatile organic solvent. In one embodiment, the lightabsorber preform solution consists of the solvent, the plurality ofcarbon nanotubes and the plurality of carbon particles, the carbonparticles are carbon black powder, and the solvent is ethanol.

When the mass of the carbon particles is too small, the absorptionperformance of the light absorber formed by spraying the light absorberpreform solution is poor. When the mass of the carbon particles is toomuch, it is difficult to spray the light absorber preform solution. Themass ratio of carbon nanotubes and carbon particles is: carbonnanotubes: carbon particles=4:5 to 4:70. The mass ratio of carbonnanotubes and carbon particles is in a range from about 4:5 to about4:70. The mass of the solvent can be adjusted according to actualconditions to ensure that the light absorber preform solution can besprayed. The solvent can be greater than or equal to about 50 mL(milliliter). In the light absorber preform solution, when the solventis about 200 mL and the carbon nanotube is about 0.4 g, the mass of thecarbon particles is in a range from about 0.5 g to about 7 g. In oneembodiment, the solvent is 200 mL, the carbon nanotube is 0.4 g, themass of the carbon particles is in a range from 0.5 g to 7 g. In oneembodiment, the ethanol solvent is 200 mL, the carbon nanotube is 0.4 g,and the carbon particle is 5 g.

A method for making the light absorber preform solution of the firstembodiment, includes one or more of the following steps:

S11, providing the plurality of carbon nanotubes;

S12, placing the plurality of carbon nanotubes into the solvent andflocculating, to obtain a carbon nanotube suspension; and

S13, adding the plurality of carbon particles into the carbon nanotubesuspension.

During step S11, the preparation method of carbon nanotubes is notlimited, such as arc discharge method, laser evaporation method, orchemical vapor deposition method. In one embodiment, the chemical vapordeposition method is used to prepare carbon nanotubes, which includesthe following steps:

S111, growing a carbon nanotube array on a growth substrate; and

S112, scraping the carbon nanotube array from the growth substrate by aknife or other similar devices, to obtain the plurality of carbonnanotubes.

During step S111, the carbon nanotube array includes the plurality ofcarbon nanotubes. The length of the plurality of carbon nanotubes in thecarbon nanotube array is not limited. In one embodiment, the lengths ofthe carbon nanotubes are greater than 100 μm (micrometers). Theplurality of carbon nanotubes is substantially parallel to each otherand substantially perpendicular to the surface of the growth substrate.The carbon nanotube array is one of a single-wall carbon nanotube array,a double-wall carbon nanotube array, and a multi-wall carbon nanotubearray. The method for making the carbon nanotube array includes thefollowing steps:

(a) providing a substantially flat and smooth growth substrate;

(b) forming a catalyst layer on the growth substrate;

(c) annealing the growth substrate with the catalyst layer in air at atemperature in the approximate range from 700 degrees Celsius to 900degrees Celsius for about 30 to about 90 minutes;

(d) heating the growth substrate with the catalyst layer to atemperature in the approximate range from 500 degrees Celsius to 740degrees Celsius in a furnace with a protective gas therein; and

(e) supplying a carbon source gas to the furnace for about 5 to about 30minutes and growing a super-aligned carbon nanotube array on the growthsubstrate.

During step (a), the growth substrate can be a P-type silicon wafer, anN-type silicon wafer, or a silicon wafer with a film of silicon dioxidethereon. In one embodiment, a 4-inch P-type silicon wafer is used as thegrowth substrate.

During step (b), the catalyst layer includes catalysts, and thecatalysts can be made of iron (Fe), cobalt (Co), nickel (Ni), or anyalloy thereof.

During step (d), the protective gas can be made up of at least one ofnitrogen (N₂), ammonia (NH₃), and a noble gas.

During step (e), the carbon source gas can be a hydrocarbon gas, such asethylene (C₂H₄), methane (CH₄), acetylene (C₂H₂), ethane (C₂H₆), or anycombination thereof. The super-aligned carbon nanotube array can have aheight more than 100 microns and include the plurality of carbonnanotubes parallel to each other and approximately perpendicular to thesubstrate. Because the length of the carbon nanotubes is very long,portions of the carbon nanotubes are bundled together. Moreover, thesuper-aligned carbon nanotube array formed under the above conditions isessentially free of impurities such as carbonaceous or residual catalystparticles. The carbon nanotubes in the super-aligned array are closelypacked together by the van der Waals attractive force. In oneembodiment, the carbon source gas is selected from acetylene and otherchemically active hydrocarbons, and the protective gas is selected fromnitrogen, ammonia or inert gas.

During step S112, the carbon nanotube array is scraped from the growthsubstrate to obtain the carbon nanotubes, and the carbon nanotubes are,to a certain degree, able to maintain the bundled state of the carbonnanotubes.

During step S12, after adding the carbon nanotubes to the solvent, aprocess of flocculating is executed to get a floccule structure. Theprocess of flocculating is selected from the group consisting ofultrasonic dispersion and high-strength agitating/vibrating. In oneembodiment, ultrasonic dispersion is used to flocculate the solventcontaining the carbon nanotubes for about 10 minutes to about 30minutes. The carbon nanotubes in the solvent have a large specificsurface area and the bundled carbon nanotubes have a large van der Waalsattractive force, the flocculation process does not completely dispersethe carbon nanotubes in the solvent, and the flocculated and bundledcarbon nanotubes are attracted to each other by the van der Waals forcesto form the network structure, which can also be called the flocculestructure. FIG. 1 is a transmission electron microscope (TEM) image ofcarbon nanotubes dispersed in the ethanol. It can be seen from FIG. 1that the carbon nanotubes of the carbon nanotube suspension areinterconnected to form the network structure. In one embodiment, thecarbon nanotube suspension consists of the solvent and the networkstructure. Furthermore, a step of adding a dispersant into the solventcan be included in the step S12. In one embodiment, the dispersant ispolyvinylpyrrolidone (PVP).

During step S13, after adding the plurality of carbon particles into thecarbon nanotube suspension, mixing can be executed. The mixing method isnot limited. In one embodiment, the mixing is performed by ultrasonicoscillation. FIG. 2 is an optical photograph of the carbon black powder.

During step S12 and step S13, the mass ratio of carbon nanotubes andcarbon particles is: carbon nanotube: carbon particles=4:5 to 4:70. Themass ratio of carbon nanotubes and carbon particles is in a range fromabout 4:5 to about 4:70. The mass of the solvent can be adjustedaccording to actual conditions to ensure that the light absorber preformsolution can be sprayed. In one embodiment, the solvent is 200 mL, thecarbon nanotubes are 0.4 g, and the carbon particles are in a range from0.5 g to 7 g. The light absorber preform solution can also be preparedby mixing carbon nanotubes and carbon particles first, and thendispersing mixture of carbon nanotubes and carbon particles into thesolvent.

The following is a specific example.

EXAMPLE 1

The carbon nanotube array with a height of 285 microns is grown on an8-inch silicon wafer, and the carbon nanotube array is scraped from thesilicon wafer and placed in the ethanol solvent. Then, PVP is added inthe ethanol solvent (0.1 g PVP per 200 mL ethanol solvent), andultrasonic flocculation is performed using an ultrasonic cell disruptor,to form the carbon nanotube suspension. Finally, the carbon black powderwith a diameter of 10 μm is added, and ultrasonic treatment is performedfor 0.5 h (hour) to obtain a stable light absorber preform solution. InExample 1, when 1 g of carbon black powder is added to the carbonnanotube suspension, the aggregation effect of the carbon nanotubes andcarbon black powders is not obvious, as shown in FIG. 3. When 5 g ofcarbon black powder is added to the carbon nanotube suspension, thecarbon nanotubes and carbon black powder aggregate together, as shown inFIG. 4, but the light absorber preform solution can still be sprayed bya spray gun, and the sprayed layer remains uniform. However, when 7 g ofcarbon black powder is added to the carbon nanotube suspension, thecarbon nanotubes and carbon black powder aggregate seriously, to form aprecipitate deposited on the bottom of the container, and theprecipitate is clearly layered with the upper liquid, as shown in FIG.5. In FIG. 5, the upper liquid is transparent, which indicates that themass of carbon nanotubes in the upper liquid is very low. Theprecipitate is a colloidal substance and cannot be used for spraying.Therefore, in the carbon nanotube suspension formed by 200 mL of ethanolsolvent and 0.4 g of carbon nanotubes, 5 g of carbon black powder is thebest ratio for spraying.

The light absorber preform solution and the method for making the lightabsorber preform solution have the following advantages: first, thelight absorber preform solution is sprayed on other objects to form thelightabsorber capable of absorbing infrared light and sunlight; second,the preparation method is simple and can be mass produced.

A light absorber of a second embodiment includes the plurality of carbonnanotubes and the plurality of carbon particles, the plurality of carbonnanotubes form the network structure, and the plurality of carbonparticles are located in the network structure. Some carbon particlesare inserted into the network structure, and surrounded or covered bythe plurality of carbon nanotubes. In one embodiment, each carbonparticle is embedded into the network structure and trapped between theentangled carbon nanotubes. The carbon particles are in direct contactwith the carbon nanotubes. For each carbon particle inserted into thenetwork structure, one portion of surface of the carbon particle is indirect contact with the carbon nanotubes, and the other portion ofsurface of the carbon particle is exposed and is spaced apart from theplurality of carbon nanotubes. In one embodiment, one portion of each ofthe plurality of carbon particles is in direct contact with theplurality of carbon nanotubes, and the other portion of each of theplurality of carbon particles is spaced apart from the plurality ofcarbon nanotubes. The carbon nanotube network structure connectsmultiple carbon particles together.

Furthermore, the lightabsorber can also include a substrate forsupporting the network structure. The substrate is used for supportingthe carbon nanotubes and the carbon particles. The type, shape, orthickness of the substrate is not limited. The substrate can be quartz,polymer, metal, ceramic, cloth or the like. The surface of the substratecan be a flat surface, a curved surface, or an irregular surface. In oneembodiment, the substrate is quartz.

A method for making the light absorber of the second embodiment,includes the following steps:

S21, providing the light absorber preform solution and

S22, spraying the light absorber preform solution.

During step S22, the spraying method is not limited. In one embodiment,the spray gun is used for spraying. The diameter of the spray gun is 1mm, the carrier gas is nitrogen with a pressure of 0.3 MPa, theeffective spray range is about 150 mm, and the solution consumption is100 mL/minute. The light absorber preform solution is sprayed on theobject, such as the substrate, a cloth, and so on.

Furthermore, after step S22, drying can be used to remove the solvent.The drying method is not limited, such as heating. In one embodiment,the solvent is ethanol, and the ethanol is completely dried within a fewminutes after spraying, without any heat treatment.

FIG. 6 shows an optical photograph of a toy, wherein the light absorberpreform solution is not sprayed on the toy. FIG. 7 is an opticalphotograph of the toy coated by the light absorber that is formed byspraying the light absorber preform solution on the toy. It can be seenfrom FIG. 7 that the light absorber preform solution can be sprayedevenly the irregular surface. In one embodiment, the light absorberpreform solution is sprayed on the quartz substrate to form the lightabsorber.

FIG. 8 to FIG. 23 show the performances of the light absorber. FIG. 8 isa scanning electron microscope (SEM) image of a coated layer formed byspraying a pure carbon nanotube dispersion, the pure carbon nanotubedispersion is formed by dispersing the pure carbon nanotubes in thesolvent, and there are only carbon nanotubes in the solvent. FIG. 9 isan SEM photograph of the quartz substrate after spraying the lightabsorber preform solution. In FIG. 9, the light absorber consists of thequartz substrate, the carbon nanotubes and the carbon particles. It canbe seen from FIG. 8 and FIG. 9 that the carbon nanotubes are effectivelyand uniformly attached to the carbon particles to form a sprayed layer,and this sprayed layer is the light absorber. Through the connection ofthe carbon nanotubes, the carbon particles are stacked with each other,some gaps are formed by the carbon particles, and some gaps are formedby the carbon nanotubes, so that the light absorber has a plurality ofpores. The light absorber is a porous structure, which improves lightabsorption.

FIG. 10 is another SEM image of the coated layer formed by spraying thepure carbon nanotube dispersion. In FIG. 10, the surface of the coatedlayer formed by the pure carbon nanotube dispersion is relatively flat,and the average surface roughness is tens of microns. FIG. 11 is an SEMimage of the light absorber. In FIG. 11, the surface of the lightabsorber maintains the undulating morphology of the surface of thecoated layer that is formed by spraying the pure carbon nanotubedispersion, and the carbon particles are uniformly distributed on thetop surface of the coated layer.

FIG. 12 is yet another SEM image of the coated layer formed by sprayingthe pure carbon nanotube dispersion, and FIG. 13 is another SEM image ofthe light absorber. It can be seen from FIG. 12 and FIG. 13 that thesurface roughness of the light absorber is greater than the surfaceroughness of the coated layer formed by spraying the pure carbonnanotube dispersion. It can be seen from FIG. 10 to FIG. 13 that theintroduction of carbon particles increases the surface roughness of thelight absorber, thereby improving the scattering and absorption of lighton the surface of the light absorber.

FIG. 14 to FIG. 16 show the reflection spectrums of the light absorberunder normal incidence and no polarization. FIG. 14 shows the reflectionspectrum of the light absorber in a visible light wavelength range (400nm-800 nm), FIG. 15 shows the reflection spectrum of the light absorberin a near-infrared wavelength range (800 nm-2 μm), and FIG. 16 shows thereflection spectrum of the light absorber in the mid-infrared.wavelength range (2 μm-20 μm).

Seen from FIG. 14 to FIG. 16 that in the wide spectrum range from thevisible light to the mid-infrared light (400 nm-20 μm), the reflectanceof the light absorber decreases with the increase of mass of the carbonparticle. The light absorber containing 5 g carbon particles has areflectivity of 0.075% in the visible wavelength range, a reflectivityof 0.05% in the near-infrared wavelength range, and a reflectivity of0.02% in the mid-infrared wavelength range. In FIG. 14-FIG. 16, theterms “CNT Spray” refers to the coated layer formed by spraying the purecarbon nanotube dispersion, and terms “CNT Array” refers to the carbonnanotube array. The reflectivity of the light absorber is lower thanthat of coated layer formed by spraying the pure carbon nanotubedispersion. The reflectivity of the light absorber is close to thereflectivity of the carbon nanotube array. The low reflectivity of thelight absorber indicates that the light absorber has good lightabsorption performance.

FIG. 17 to FIG. 20 show the reflection spectrums of the light absorberwhen an incident angle of an incident light is 0 degrees to 60 degrees.The incident angle refers to an angle between an incident light and anormal line, wherein the normal line is perpendicular to the surface ofthe light absorber. FIG. 17 shows a reflectance spectrum of the lightabsorber when the incident angle is 15 degrees, FIG. 18 shows areflectance spectrum of the light absorber when the incident angle is 30degrees, FIG. 19 shows a reflectance spectrum of the light absorber whenthe incident angle is 45 degrees, and FIG. 20 shows a reflectancespectrum of the light absorber when the incident angle is 60 degrees.Seen from FIG. 17 to FIG. 20 that the light absorber has approximatelythe same reflectivity at different incident angles, which indicates thatthe reflectivity of the light absorber has nothing to do with theincident angle. Thus, the light absorber has excellent omnidirectionalabsorption performance in the visible wavelength range. The“omnidirectional absorption” means that the light absorber has a highabsorptivity at each incident angle.

In FIG. 20, the light absorber containing 5 g of carbon particles has anabsorption rate of more than 99.9% at the incident angle of 60 degrees,which is almost the same as the absorption rate of the CNT array.Therefore, the light absorber achieves an omnidirectional highabsorption efficiency of 99.9% in the wide wavelength range of 400 nm to20 μm, regardless of the incident angle.

FIG. 21 shows a thermal imager photograph of the light absorbercontaining 5 g of carbon particles (spraying the light absorber preformsolution on the silicon substrate). FIG. 22 shows a time-temperature ofthe light absorber containing 5 g of carbon particles (spraying thelight absorber preform solution on the silicon substrate) when exposingthe light absorber to sunlight, and the heating behavior of the lightabsorber under solar radiation is studied. The solar simulator is usedas a solar radiation source, the standard. power density of the solarsimulator is 1000 W/m², and the temperature of the light absorber ismonitored by a mid-infrared thermal imager. In FIG. 21, the sample (thelight absorber containing 5 g of carbon particles) cannot bedistinguished from the surrounding environment at first; after 0.5seconds, the sample will absorb sunlight and the temperature of thesample will start to rise, at this time, the sample can be dearlydistinguished from the surrounding environment; and as time increases,the temperature of the sample will increase until the temperature of thesample remains stable. FIG. 22. shows the temperature change of thesample recorded by a mid-infrared thermal imager with time, in which thecoated layer formed by spraying the pure carbon nanotube dispersion andthe silicon substrate with the light absorber are compared. From thepoint of view of the heating rate and equilibrium temperature, the lightabsorber containing 5 g carbon particles is the best.

FIG. 23 shows an optical photograph of the quartz substrate afterspraying the light absorber preform solution on the quartz substrate.FIG. 24 shows a thermal image captured by an infrared thermal imagerunder the irradiation of the solar simulator. Seen from FIG. 23 and FIG.24, the light absorber can absorb sunlight and can collect the heat ofsunlight. FIG. 21 to FIG. 24 show that the light absorber has good solarheat collection performance.

FIG. 25 shows an optical photograph of a water droplet falling on asurface of the light absorber. It can be seen from FIG. 25 that thecontact angle between the light absorber containing 5 g of carbonparticles and the water droplet reaches 165 degrees, and the waterdroplets are easy to roll off, indicating that the light absorber hasexcellent super-hydrophobic performance, the wettability can be keptstable, and the surface of the light absorber is not be damaged. Whenthe water droplets slip off the surface of the light absorber, dust anddirt will be removed with the water droplets, indicating that lightabsorber has good self-cleaning performance.

The light absorber and the method for making the light absorber have thefollowing advantages: first, the light absorber preform solution can besprayed on curved, irregularly shaped or uneven surfaces; second, thelight absorber is composed of carbon nanotubes and carbon particles, andthe light absorber consists of carbon material, which can avoid theinfluence of other materials on the absorption of sunlight and infraredlight; third, the introduction of carbon particles improves the surfaceroughness of the light absorber and increases the absorption rate oflight; fourth, the light absorber consists of carbon material, thus thelight absorber has good absorption performance in the wide wavelengthrange (400 nm-20 μm), and the absorption rate is 99.9%; fifth, the lightabsorber has excellent omnidirectional absorption performance in thewide wavelength range (400 nm-20 μm), and has nothing to do with theincident angle; sixthly, the light absorber has excellentsuper-hydrophobic characteristics and good self-cleaning performance.

FIG. 26 shows an infrared detector 100 of a third embodiment. Theinfrared detector 100 includes an infrared light absorber 110, athermoelectric element 112, and an electrical signal detecting element114. The infrared light absorber 110 is located on and in direct contactwith the thermoelectric element 112. The infrared light absorber 110includes the plurality of carbon nanotubes, and length extendingdirections of the carbon nanotubes are parallel to the contact surfacebetween the thermoelectric element 112 and the infrared light absorber110. The electrical signal detecting element 114 is electricallyconnected to the thermoelectric element 112 by conductive wires. Theelectrical signal detecting element 114 and the thermoelectric element112 are connected in series to form a loop for detecting a change of anelectrical signal of the thermoelectric element 112.

The infrared light absorber 110 is formed by spraying the light absorberpreform solution on the thermoelectric element 112, and the infraredlight absorber 110 is the light absorber of the second embodiment above.

The infrared light absorber 110 is configured to absorb infrared lightand convert the infrared light into heat. The infrared light absorber110 has a high absorption rate for the infrared light. A temperature ofthe infrared light absorber 110 increases when the infrared lightabsorber 110 absorbs the infrared light. Since the carbon nanotubes havea high thermal conductivity, the infrared light absorber 110 cantransfer the heat to the thermoelectric element 112. When thethermoelectric element 112 absorbs the heat, a temperature of thethermoelectric element 112 increases, so that the electrical performanceof the thermoelectric element 112 can be changed.

The thermoelectric element 112 may be a pyroelectric element, athermistor, or a thermocouple element. A material of the pyroelectricelement has a high thermoelectric coefficient, such as lead zirconatetitanate-based ceramics, lithium tantalate, lithium niobate,triglyceride sulfate, and the like. The thermistor may be asemiconductor thermistor, a metal thermistor, an alloy thermistor, orthe like. In one embodiment, a material of the thermoelectric element112 is lead zirconate titanate-based ceramic.

The electrical signal detecting element 114 is used to detect the changein the electrical signal of the thermoelectric element 112. Theelectrical signal detecting element 114 may be selected according to thethermoelectric element 112. In one embodiment, the thermoelectricelement 112 is the pyroelectric element, the increased temperature ofthe thermoelectric element 112 causes a voltage or a current to appearat both ends of the pyroelectric element, and the electrical signaldetecting element 114 is a current-to-voltage converter and configuredto detect the change of the voltage or current of the thermoelectricelement 112. In another embodiment, the thermoelectric element 112 isthe thermistor, a resistance of the thermistor is changed by increasinga temperature of the thermistor; and the electrical signal detectingelement 114 including a power supply and a current detector isconfigured to detect the change of the current, so that a change of theresistance of the electrical signal detecting element 114 can bedetected. In another embodiment, the thermoelectric element 112 is thethermocouple element, the infrared light absorber 110 should be disposedat only one end or one part of the thermocouple element. Thus, atemperature difference can be generated between two ends of thethermocouple element, and the temperature difference leads to apotential difference between the two ends of the thermocouple element.The electrical signal detecting element 114 is a voltage detector andconfigured to detect the potential change of the thermocouple element.

When the infrared detector 100 is in operation, the infrared lightirradiates the infrared light absorber 110 (the light absorber above),the carbon nanotubes convert the infrared light into the heat andtransfer the heat to the thermoelectric element 112; the temperature ofthe thermoelectric element 112 raises after absorbing the heat, andelectrical properties such as resistance, current, or voltage of thethermoelectric element 112 are changed; and the electrical signaldetecting element 114 detects a change of the electrical properties ofthe thermoelectric element 112, so that the infrared light can bedetected.

The infrared detector 100 has the following advantages: first, theinfrared light absorber 110 has a good absorption performance in thenear-infrared wavelength range (800 nm-2 μm) and the mid-infraredwavelength range (2 μm-20 μm), thereby improving the responsivity andsensitivity of the thermoelectric element 112, so that the infrareddetector 100 has a higher sensitivity; second, the infrared lightabsorber 110 has an omnidirectional absorption performance that is notaffected by different polarization of light, thereby expanding theapplication fields of the infrared detector 100.

FIG. 27 shows an infrared imager 200 of the third embodiment. Theinfrared imager 200 includes an infrared receiver 210, an infrareddetector assembly 220, a signal processor 230, and an infrared imagedisplay 240. The infrared receiver 210 is configured to receive infraredlight and transfer the infrared light to the infrared detector assembly220. The infrared detector assembly 220 is configured to convert theinfrared light into an electrical signal and transfer the electricalsignal to the signal processor 230. The signal processor 230 isconfigured to process the electrical signal to obtain thermal fielddistribution data. The infrared image display 240 is configured todisplay an infrared thermal image according to the thermal fielddistribution data.

The infrared receiver 210 is configured to receive the infrared lightemitted by an object. In one embodiment, the infrared receiver 210 isthe infrared lens. After the infrared light emitted by the object isreceived and converged by the infrared lens, the infrared light isdirectly transferred to the infrared detector assembly 220. It can beunderstood that the infrared receiver 210 can be omitted.

The infrared detector assembly 220 includes a plurality of the infrareddetectors 100. The plurality of the infrared detectors 100 are arrangedto form a two-dimensional array, and each of the plurality of theinfrared detectors 100 can convert the infrared light into theelectrical signal. The each of the infrared detector 100 is equivalentto one pixel, and the each of the infrared detector 100 converts theinfrared radiation into the electrical signal. Thus, the infrareddetector assembly 220 can detect the infrared light emitted by theobject. A distance between any two adjacent infrared detectors 100 canbe selected according to the thermal imaging resolution.

The signal processor 230 is configured to process the electrical signalof each infrared detector 100 to obtain the thermal field distributiondata of the object. The signal processor 230 can calculate temperaturedata of each corresponding surface position of the object according tothe change of the electrical signal of each infrared detector 100. Thetemperature data can form the thermal field distribution data of theobject. Thus, the signal processor 230 can calculate the thermal fielddistribution data by the electrical signal of each infrared detector100.

The infrared image display 240 is configured to display the infraredthermal image according to the thermal field distribution data.Different temperatures can be displayed in different colors in theinfrared thermal image. The infrared thermal image corresponds to thetemperature distribution of the object. Thus, the infrared thermal imagecan reflect a temperature of each position of the object. For example,when the infrared imager 200 is used in a medical field, a human bodycan be thermally imaged by the infrared imager 200, thus doctors candetermine the disease and the extent of the disease in different partsof the body according to the thermal image, thereby providing a basisfor clinical diagnosis.

When the infrared imager 200 is in operation, the infrared light emittedby the object is received by the infrared receiver 210; the infraredreceiver 210 receives the infrared light and transfers the infraredlight to the infrared detector assembly 220; the infrared detectorassembly 220 converts the infrared light into the electrical signals andtransmit the electrical signals to the signal processor 230; the signalprocessor 230 processes and calculates the electrical signals to obtainthe thermal field distribution data; the infrared image display 240displays the infrared thermal image of the object according to thethermal field distribution data.

The infrared imager 200 has the following advantages: first, theinfrared light absorber 110 has a good absorption performance in thenear-infrared wavelength range (800 nm-2 μm) and the mid-infraredwavelength range (2 μm-20 μm), thereby improving the responsivity andsensitivity of the thermoelectric element 112, so that the infraredimager 200 has a higher sensitivity; second, the infrared light absorber110 has an omnidirectional absorption performance that is not affectedby different polarization of light, thereby expanding the use range ofthe infrared imager 200.

FIG. 28 shows an infrared stealth cloth 300 of a fourth embodiment. Theinfrared stealth cloth 300 includes a cloth substrate 310 and theinfrared light absorber 110 located on the cloth substrate 310. Theinfrared light absorber 110 is formed by spraying the light absorberpreform solution on the cloth substrate 310, and the infrared lightabsorber 110 is the light absorber of the second embodiment above. Theinfrared light absorber 110 may be located between two cloth substrates310 to form a sandwich structure. The plurality of carbon nanotubes isparallel to a surface of the infrared light absorber 110 close to thecloth substrate 310.

The infrared light absorber 110 can be in direct contact with the clothsubstrate 310. In one embodiment, the cloth substrate 310 defines athrough hole or multiple through holes (not shown), and the infraredlight absorber 110 is suspended on the through holes of the clothsubstrate 310. A material of the cloth substrate 310 is not limited, andthe material such as cotton, polyester, silk, wool, hemp, or leather maybe used. In one embodiment, the infrared light absorber 110 is sewnbetween two cloth substrates 310.

FIG. 29 shows an optical photograph of the infrared stealth cloth 300.Seen from FIG. 29, the infrared stealth cloth 300 has good flexibility.The infrared stealth cloth 300 has a low density of 3×10⁻⁶ g/mm², isultra-light, and can be used in space or military fields.

FIG. 30 shows an optical photograph of a hand covered by the infraredstealth cloth 300. FIG. 31 shows a thermal image of the hand covered bythe infrared stealth cloth 300. Seen from FIG. 30 and FIG. 31, when thehand is covered by the infrared stealth cloth 300, infrared lightemitted by the hand is absorbed by the infrared stealth cloth 300. Thus,the infrared light emitted by the hand cannot pass through the infraredstealth cloth 300 and be detected by an infrared light system. Thus, theinfrared stealth cloth 300 has a good stealth effect.

FIG. 32 shows infrared stealth clothes 400 of the fourth embodiment. Atleast a portion of the infrared stealth clothes 400 is made of theinfrared stealth cloth 300. The whole infrared stealth clothes 400 canbe made of the infrared stealth cloth 300, or a portion of the infraredstealth clothes 400 is made of the infrared stealth cloth 300. Theinfrared stealth clothes 400 are not limited to clothes, and theinfrared stealth clothes 400 can be a glove, a mask, or the like. Theclothes, glove, mask can be collectively referred to as the infraredstealth clothes 400. In another embodiment, the infrared stealth clothes400 include a clothes body 410, and at least a portion of the clothesbody 410 is made of the infrared stealth cloth 300.

The infrared stealth cloth 300 and the infrared stealth clothes 400 havethe following advantages: first, the infrared light absorber 110 has agood absorption performance in the near-infrared wavelength range (800nm-2 μm) and the mid-infrared wavelength range (2 μm-20 μm), so that theinfrared stealth cloth 300 and the infrared stealth clothes 400 have agood stealth effect; second, the infrared light absorber 110 has anomnidirectional absorption performance that is not affected by differentpolarization of light, thereby expanding the use range and improving thestealth effect of the infrared stealth cloth 300 and the infraredstealth clothes 400.

Since the infrared light absorber 110 in the infrared stealth cloth 300has a good ability to absorb sunlight, the infrared stealth cloth 300can also be prepared into sunshade tools such as sun umbrellas.

Referring to FIG. 33, a solar heat collector 500 of a fifth embodimentincludes a container 502, a transparent cover plate 504, a thermalinsulation material 506 and a heat absorption plate 508. The container502 defines an opening, and in one embodiment, the opening is located onthe top of the container 502. The transparent cover plate 504 is locatedat the opening of the container 502, or the transparent cover plate 504covers the opening of the container 502, so that sunlight can passthrough the transparent cover plate 504 and enter inside of thecontainer 502. The thermal insulation material 506 is located inside ofthe container 502 and forms an insulation space. In one embodiment, thethermal insulation material 506 is located on the inner side of thecontainer 502 so that the insulation space is located inside of thecontainer 502. The heat absorption plate 508 is located in theinsulation space. In one embodiment, the heat absorption plate 508 issuspended in the insulation space. The heat absorption plate 508includes a plurality of fluid channels 5084 to facilitate the passage offluid. The type of the fluid is not limited, and in one embodiment, thefluid is water.

The heat absorption plate 508 includes a base 5080 and a coating 5082located on the base 5080. The coating 5082 is the light absorber of thesecond embodiment above, the coating 5082 and the light absorber abovehave the same structure and performance. Thus, the coating 5082 includesthe plurality of carbon nanotubes and the plurality of carbon particles,the plurality of carbon nanotubes form the network structure, and theplurality of carbon particles are located in the network structure. Eachcarbon particle inserted into the network structure is surrounded orcovered by the plurality of carbon nanotubes, and the carbon particlesare in direct contact with the carbon nanotubes. The carbon nanotubenetwork structure connects multiple carbon particles together. Thecoating 5082 may be located on the entire surface of the base 5080, orlocated on the surface of the base 5080 close to the transparent coverplate 504. The coating 5082 is in direct contact with the base 5080. Thecoating 5082 is formed by spraying the light absorber preform solutionon the base 5080. The plurality of fluid channels 5084 are defined inthe base 5080. In one embodiment, the extending directions of the fluidchannels 5084 are parallel to a contact surface between the base 5080and the coating 5082.

The material of the container 502 is not limited. In one embodiment, thematerial of the container 502 is metal. The transparent cover plate 504can be made of a material with high light transmittance. In oneembodiment, the transparent cover plate 504 is a glass cover plate. Thethermal insulation material 506 may be asbestos, foam, or the like. Thematerial of the base 5080 is not limited, such as metal, carbon nanotubefilm, quartz, silicon dioxide, and so on. In one embodiment, thematerial of the base 5080 is metal.

The solar heat collector 500 also includes some small elements to fastenthe above-mentioned elements together, and these small elements includescrews, nuts and the like.

Sunlight irradiates the heat absorption plate 508 through thetransparent cover plate 504. The heat absorption plate 508 absorbs thesolar radiation energy, converts the solar radiation energy into heatenergy, and transmits the heat energy to the fluid in the fluid channels5084, so that the fluid is heated by the heat energy.

Referring to FIG. 34, a solar water heater 600 of the fifth embodimentincludes the solar heat collector 500, a water inlet pipe 602, a wateroutlet pipe 604 and a water storage container 606. The water inlet pipe602 is connected to one end of the fluid channel 5084, and the wateroutlet pipe 604 is connected to the other end of the fluid channel 5084.One end of the water outlet pipe 604 is connected to the fluid channel5084, and the other end of the water outlet pipe 604 is connected to thewater storage container 606. Fluids such as water flow into the fluidchannels 5084 from the water inlet pipe 602, flow into the water outletpipe 604 from the fluid channels 5084, and then flow into the waterstorage container 606 from the water outlet pipe 604. In one embodiment,the base 5080 includes the plurality of fluid channels 5084, one end ofeach fluid channel 5084 is connected to the water inlet pipe 602, andthe other end of each fluid channel 5084 is connected to the literoutlet pipe 604.

The water storage container 606 further includes an outlet (not shown inthe figure), the water in the water storage container 606 can flow outthrough the outlet of the water storage container 606.

Furthermore, a thermal insulation layer can be located on and enclosedthe water outlet pipe 604 and the water storage container 606, so thatthe warm water or hot water flowing through the water outlet pipe 604and the water storage container 606 is kept warm or hot. The material ofthe thermal insulation layer is the same as the thermal insulationmaterial 506.

When the solar water heater 600 is in operation, sunlight is irradiatedon the heat absorption plate 508 through the transparent cover plate504, and the solar radiation energy is absorbed by the heat absorptionplate 508. The heat absorption plate 508 converts the solar radiationenergy into the heat energy, and transmitted the heat energy to thefluid channels 5084. In this way, the cold water in the fluid channels5084 that is from the water inlet pipe 602 is heated by the heat energyof the fluid channels 5084, and the temperature of the water graduallyrises, so that the cold water becomes warm water or hot water. Then thewarm water or hot water flows into the water storage container 606 fromthe water outlet pipe 604, waiting for use.

The solar heat collector 500 and the solar water heater 600 have thefollowing advantages: first, because the coating 5082 has excellentomnidirectional light absorption performance, the heat collectionperformances of the solar heat collector 500 and the solar water heater600 can be improved, the heat absorption rates of the solar heatcollector 500 and the solar water heater 600 are increased, and the heatloss of sunlight is reduced; Second, the coating 5082 has excellentsuper-hydrophobic properties and good self-cleaning performance, whichprolongs the service life of the solar collector 500 and the solar waterheater 600.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Additionally, it is also to be understood that the above description andthe claims drawn to a method may comprise some indication in referenceto certain steps. However, the indication used is only to be viewed foridentification purposes and not as a suggestion as to an order for thesteps.

What is claimed is:
 1. A solar heat collector, comprising: a container;a transparent cover plate on the container; a thermal insulationmaterial inside of the container to form an insulation space; and a heatabsorption plate in the insulation space, wherein the heat absorptionplate comprises a base and a coating on the base, and the coatingcomprises a plurality of carbon nanotubes entangled with each other toform a network structure and a plurality of carbon particles in thenetwork structure.
 2. The solar heat collector of claim 1, wherein eachof the plurality of carbon particles is embedded into the networkstructure.
 3. The solar heat collector of claim 1, wherein the pluralityof carbon nanotubes are in direct contact with the plurality of carbonparticles.
 4. The solar heat collector of claim 3, wherein one portionof each of the plurality of carbon particles is in direct contact withthe plurality of carbon nanotubes, and the other portion of each of theplurality of carbon particles is spaced apart from the plurality ofcarbon nanotubes.
 5. The solar heat collector of claim 1, wherein thecoating consists of the plurality of carbon nanotubes and the pluralityof carbon particles.
 6. The solar heat collector of claim 1, wherein theplurality of carbon nanotubes are multi-walled carbon nanotubes with anaverage diameter of 20 nm.
 7. The solar heat collector of claim 1,wherein the container defines an opening, and the transparent coverplate covers the opening.
 8. The solar heat collector of claim 1,wherein a plurality of fluid channels are defined in the base, andextending directions of the plurality of fluid channels are parallel toa contact surface between the base and the coating.
 9. The solar heatcollector of claim 1, wherein a mass ratio of the plurality of carbonnanotubes and the plurality of carbon particles is in a range from about4:5 to about 4:70.
 10. The solar heat collector of claim 1, wherein thecoating is formed by spraying a light absorber preform solution on thebase, and the light absorber preform solution comprises a solvent, theplurality of carbon nanotubes, and the plurality of carbon particles.11. A solar water heater, comprising: a solar heat collector, comprisinga container; a transparent cover plate on the container; a thermalinsulation material inside of the container to form an insulation space;and a heat absorption plate in the insulation space, wherein the heatabsorption plate comprises a base and a coating on the base, a pluralityof fluid channels are defined in the base, and the coating comprises aplurality of carbon nanotubes entangled with each other to form anetwork structure and a plurality of carbon particles in the networkstructure; a water storage container; a water inlet pipe connected tothe plurality of fluid channels; and a water outlet pipe, wherein oneend of the water outlet pipe is connected to the plurality of fluidchannels, and the other end of the water outlet pipe is connected to thewater storage container.
 12. The solar water heater of claim 11, whereineach of the plurality of carbon particles is embedded into the networkstructure.
 13. The solar water heater of claim 11, wherein the pluralityof carbon nanotubes are in direct contact with the plurality of carbonparticles.
 14. The solar water heater of claim 13, wherein one portionof each of the plurality of carbon particles is in direct contact withthe plurality of carbon nanotubes, and the other portion of each of theplurality of carbon particles is spaced apart from the plurality ofcarbon nanotubes.
 15. The solar water heater of claim 11, wherein thecoating consists of the plurality of carbon nanotubes and the pluralityof carbon particles.
 16. The solar water heater of claim 11, wherein theplurality of carbon nanotubes are multi-walled carbon nanotubes with anaverage diameter of 20 nm.
 17. The solar water heater of claim 11,wherein the container defines an opening, and the transparent coverplate covers the opening.
 18. The solar water heater of claim 11,wherein a plurality of fluid channels are defined in the base, andextending directions of the plurality of fluid channels are parallel toa contact surface between the base and the coating.
 19. The solar waterheater of claim 11, wherein a mass ratio of the plurality of carbonnanotubes and the plurality of carbon particles is in a range from about4:5 to about 4:70.
 20. The solar water heater of claim 11, wherein thecoating is formed by spraying a light absorber preform solution on thebase, and the light absorber preform solution comprises a solvent theplurality of carbon nanotubes, and the plurality of carbon particles.